Systemic sclerosis with concurrent ANCA-positive IgA nephropathy successfully managed with rituximab and mycophenolate mofetil: a case report

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy and fibrosis, whereas antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a small-vessel vasculitis that frequently involves the kidneys and lungs. Although an overlap between SSc and AAV has been reported, ANCA-positive IgA nephropathy (IgAN) in SSc has not been described. Clinically, ANCA-positive IgAN resembles AAV, posing challenges for disease classification and management. However, the optimal treatment strategy for such overlapping cases has not yet been established. We report the case of a 73-year-old woman with long-standing SSc and interstitial lung disease who developed rapidly progressive glomerulonephritis. She was positive for myeloperoxidase-ANCA, and renal biopsy demonstrated crescentic glomerulonephritis with mesangial IgA and C3 deposition, raising the possibility of concomitant IgAN. The patient was treated with glucocorticoids (GCs) and rituximab (RTX) as induction therapy, followed by mycophenolate mofetil (MMF) as maintenance therapy, resulting in a marked reduction in proteinuria and stabilization of renal function. This case underscores the importance of considering ANCA-positive IgAN in SSc patients presenting with renal dysfunction and suggests that combination therapy with RTX and MMF may represent a feasible therapeutic option for this rare overlap condition.